The present invention relates generally to cotton harvesters, and more specifically to cotton-cleaning structure for a mobile cotton harvester.
Cotton is typically harvested with either a spindle-type harvester or a stripper-type harvester. The spindle-type harvester provides a much cleaner harvested crop of cotton than does the stripper-type, but the stripper-type harvester is lower in cost, has a higher capacity and has a higher harvesting efficiency than the spindle-type. Because of the advantages of the stripper in many locations, its popularity has increased even though trash content of the harvested cotton may be as high as fifty percent since sticks, burrs, leaves, soil, weeds and other trash are easily conveyed into the receptacle along with the removed cotton. The cotton gins which process stripper-harvested cotton require elaborate cleaning systems, and the pollution caused by the high trash content of the harvested cotton is a problem. The ginning rate decreases as trash content increases. The high trash content results in higher transportation and cleaning costs which translate into reduced income for the cotton producer. The trash content of the stripped cotton also increases storage problems due to the higher moisture content of the uncleaned cotton.
To reduce the trash content of the harvested cotton, field-cleaning machines are available which are mounted on the frame of the cotton stripper. The machines include a cleaning cabinet with saw-grid type cleaners extending the width of the cabinet. Typically the cabinet is positioned between the rear of the cotton stripper cab and the front portion of the cotton stripper basket, and the air duct which conveys the cotton from the harvesting unit up to the basket is fitted with pivoting grate structure which either directs the cotton into the cleaning cabinet or alternately directly into the top forward portion of the basket. Cotton directed into the cleaner is distributed over channel saws which extend around cylinders rotatably mounted between the sides of the cabinet. As the cotton and trash are drawn around by the cylinders and impact against the grid bars, the trash tends to separate from the cotton. The cleaned cotton is doffed from the channel saws on the cylinders and is conveyed up to the basket through a rear duct.
The field-cleaning machine must be economical and must have sufficient capacity so that it does not severely limit the overall capacity of the cotton stripper and field-cleaning machine combination. Several problems exist with current field-cleaning machines for cotton strippers. A primary problem is the inability of such systems to economically and effectively distribute the cotton to be cleaned uniformly over the width of the cylinders. The maximum capacity of the field-cleaning machine can only be achieved if the cotton is uniformly distributed across the cylinders. Heretofore, however, such uniform distribution could not be achieved without relatively elaborate buffer chambers or spreading devices which not only add to the weight, complexity and expense of the system, but also require a relatively large amount of space on the harvester frame.
The spreading of the cotton across the width of the cleaning machine is also very dependent upon the conveying characteristics of the upwardly and rearwardly cotton conveying duct which feeds the input of the cleaning machine. Without a reasonably uniform distribution across the width of the duct near the input to the cleaning machine, proper distribution across the width of the machine is severely hindered.
Another problem with the previously available cleaning machines is lack of a convenient and economical system for bypassing the cleaner to permit full harvester capacity when the cleaning machine can not keep up with the stripper output. The amount of cotton entering the cleaning machine depends upon the rate of travel of the stripper and the yield of the cotton in the field being stripped, and is quite dependent upon the operator of the machine. Therefore, a bypass system should be convenient to control so the operator can change between modes of operation easily and effectively.
Gumming caused by green bolls entering the cleaning machine has been a continuing problem. Time-consuming cleaning operations must be performed regularly to keep the machine operaling effeciently if green bolls consistently reach the channel saws. Productivity of the cleaning machine is reduced
as the amount of trash and green bolls which enters the machine increases.